High-pressure electric discharge lamp



Dec. 14, 1954 o. NEUNHOEFFER ET AL 2,697,183

HIGH-PRESSURE ELECTRIC DISCHARGE LAMP Filed Oct. 16, 1950 Jmkentors:

2,697,183 Patented Dec. 14, 1954 2,697,183 HIGHvPRESSUREELEtZTRICDISCI-IARGE LAlVlP Otto Neunhoetrer, Berlin-Erich, and Paul.Schulz, Karlsruhe {Baden}, Germany, assignors toPatent-Treuhand--.Geselischaft fiir eielttrisclie Gluhlampenm. b. H., a

corporation of Germany Application October16, 195 0,SerialNo. 190,264 6Claims (Clag313'184) This invention relates to a high pressure electricdischarge lamp and more particularly to a high pressure discharge lampcontaining a filling of rare gases at a pressure of more than 1atmosphere.

The usual life of such an electric discharge lamp with or sputtered offthe electrodes is deposited on the wall of the envelope and blackens it.

An object of our invention is to provide a high pressure discharge lampwhich is essentially free from blackening deposits on the inner wall ofthe envelope during a long time of lamp operation.

A further object of the invention is to bring the particles evaporatingor sputtering off the glow electrodes back to the surface of theelectrodes.

A further object is to enable a high temperature of the electrodes by astrong power input without blackening the lamp wall and evaporate at alarge degree.

A still further object is a high pressure discharge lamp so positionedthat its radiation in the direction of the upper part of the envelopecan be used although the convection current of the gas filling tendspreferably to blacken the upper part of the lamp.

ther objects of our invention will become apparent when reading thefollowing specification taken in connection with the drawing, whichshows an electric high pressure discharge lamp in a sectional view.

The spherical envelope 1 of the lamp in Fig. 1 consists of high meltingglass or quartz. The vacuumtight embedded leading-in-wires 2 bear theincandescent electrodes 3 preferably of tungsten. The high pressuredischarge lamp may be filled with krypton and Xenon at atmospheres orwith argon and some mercury. In the latter case the high inner pressurearises after evaporation of the mercury by means of the high temperatureduring the operation of the lamp. The quartz envelope 1 has an internaldiameter of about mm. and shows a Wall thickness of 24 mm.

By means of the ballast 4 the vacuumtight sealed leads 2 of theincandescent electrodes 3 are connected to a suitable voltage source 5which is sufiiciently high to start the lamp. For starting the lampspecial auxiliary electrodes may be provided in known manner. Each mainelectrode may be also connected to two leads for the purpose ofpreheating.

The ballast 4 is adjusted in such a manner that there results anoperating current of e. g. 8 amps. when the lamp is filled with mercuryand of 20 amps. when filled with krypton or Xenon. During operation ofthe lamp the incandescent electrodes 3 will have a high temperature ofe. g. more than 1000 C. and tend to evaporate or to sputter. Theevaporated particles incline to deposit on the cooler parts of the lamppreferably on the inner wall of the envelope. The resulting depositweakens extremely the radiation of the lamp. This is prevented by addingto the lamp filling a little quantity of chlorine, bromine or iodine thepartial pressure of which is about 0.05 mm. mercury during lampoperation. If the radiation of the halogen gases in the dischargepassage is to be prevented their partial pressure should not be higherthan 10 mm. mercury.

The wall temperature of the envelope 1 shall not exceed 700 C. toprevent there a chemical decomposition of the compound of the halogengases with the evaporated material. But the wall temperature must be atleast 250 the glow electrodes.also called incandescent or hotelectrodes-wh1le the halogen gas e. g. chlorine will be again free. Inconsequence of the convection currents of the evaporated par- By thiscyclic continuous which What we claim as new and desire to secure byLetters Patent of the United States is:

l. A high pressure electric an envelope of high melting gaseous fillingat a pressure discharge lamp comprising vitreous material, an inertbetween 10 and 40 atms.

and to decompose at the higher temperature adjacent to the electrodessettling said particles again onto said electrodes.

2. A high pressure electric discharge lamp comprising an envelope ofhigh melting vitreous material, an inert gaseous filling at a pressurebetween 10 and 40 atms. therein consisting of rare gas such as krypton,Xenon, said envelope containing incandescent electrodes of tungsten, andalso containing besides said inert gaseous filling a little quantity ofhalogen gas of low partial pressure, the halogen gas operating tocombine at the inner wall temperatures of said envelope with thevaporized or sputtered tungsten particles of the electrodes and todecompose at the higher temperatures adjacent to the electrodes, therebysettling said tungsten particles again onto said electrodes.

3. A high pressure electric discharge lamp comprising an envelope ofhigh melting vitreous material, an inert gaseous filling at a pressurebetween 10 and 40 atms. therein consisting of rare gas, said envelopecontaining incandescent electrodes of tungsten, and also containingbesides said inert gaseous filling a little quantity of halogen gas at apartial pressure of 0.01-10 mm. mercury during lamp operation, thehalogen gas operating to combine at the inner wall temperatures of saidenvelope with the vaporized or sputtered tungsten particles of theelectrodes and to decompose at the higher temperatures adjacent to theelectrodes, thereby settling said tungsten particles again onto saidelectrodes.

4. A high pressure electric an envelope of high melting vitreousmaterial, an inert gaseous filling at a pressure between 10 and 40 atms.therein consisting of rare gas, said envelope containing incandescentelectrodes of tungsten, and also containing besides said inert gaseousfilling a little quantity of chlodischarge lamp comprising 'rine gas ata partial pressure of 0.0110 rnercury during lamp operation, thechlorine gas operating to combine with vaporized or sputtered tungstenparticles of the electrodes forming tungsten hexachloride, thehexachloride operating to decompose adjacent to the electrodes settingfree tungsten atoms to condense onto the electrodes and further settingfree chlorine atoms.

5. A high-pressure electric discharge lamp comprising an envelope ofhigh melting vitreous material, an inert gaseous filling at a pressureexceeding 1 atrn. therein, said envelope containing incandescentelectrodes of metal, and also containing besides said inert gaseousfilling a little quantity of halogen gas, the halogen gas operating tocombine at the inner wall temperature of said envelope with vaporized orsputtered particles of said electrodes and to decompose at the highertemperature adjacent to the electrodes settling said particles againonto said electrodes, said envelope being sized with relation to thewatts con sumed by the lamp as to limit said inner wall temperaturesbetween 250700 C. during lamp operation.

6. A high-pressure electric discharge lamp comprising an envelope ofhigh melting vitreous material, an inert gaseous filling ata pressureexceeding 1 atrn. therein, said envelope conta1n1ng 1ncandescentelectrodes of metal and also containing besides said inert gaseousfilling a little quantity of halogen gas, blue at the inner walltemperature of said envelope with the halogen gas operating tocomvaporized or sputtered particles of said electrodes and to decomposeat the higher temperature adjacent to the electrodes settling saidparticles again onto said electrodes said envelope sumed by the between250-700 C. during lamp operation, trodes being sized as to exceed atemperature of 1000 during lamp operation.

References Cited in the file of this patent being sized with relation tothe watts con lamp as to limit said inner wall temperatures said elec-C.

UNITED STATES PATENTS Name Date Rentschler Sept. 2, 1941 Dellian Mar.10, 1942 Francis Feb. 1, 1949

1. A HIGH PRESSURE ELECTRIC DISCHARGE LAMP COMPRISING AN ENVELOPE OFHIGH MELTING VITREOUS MATERIAL, AN INERT GASEOUS FILLING AT A PRESSUREBETWEEN 10 AND 40 ATMS. THEREIN CONSISTING OF A RARE GAS, SAID ENVELOPECONTAINING INCANDESCENT ELECTRODES OF HIGH MELTING METAL AND ALSOCONTAINING BESIDES SAID INERT GASEOUS FILLING A LITTLE QUANTITY OFHALOGEN GAS OF LOW PARTIAL PRESSURE, THE HALOGEN GAS OPERATING TOCOMBINE AT THE WALL TEMPERATURES OF SAID ENVELOPE WITH VAPORIZED ORSPUTTERED PARTICLES OF THE ELECTRODES AND TO DECOMPOSE AT THE HIGHERTEMPERATURE ADJACENT TO THE ELECTRODES SETTLING SAID PARTICLES AGAINONTO SAID ELECTRODES.